JPH01292411A - Band gap reference voltage circuit - Google Patents

Abstract

PURPOSE:To make the temperature characteristic of an output reference voltage from a band gap reference voltage circuit flat by connecting a resistor in parallel with a diode in a band gap current generating circuit. CONSTITUTION:The band gap reference voltage circuit is constituted so as to generate an output reference voltage to an output terminal 2 in accordance with a constant current obtained from a constant current source 1. The output voltage of the output terminal 2 is expressed by the sum of a voltage VBE3 between the base and emitter of a transistor (TR) 3 and a voltage between both the ends of a resistor R4 and V=VBE3+(R4/R3)(kT/q)ln(I1/I2) is formed, and when a current is selected so that the 2nd term is positive and I1>I2 is formed because the VBE3 has a negative temperature factor, the whole temperature coefficient can be made equal to zero. In this case, the prescribed resistor may be connected in parallel with the diode 13 in order to make the temperature characteristic of the output reference voltage flat.

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a bandgap reference voltage circuit,
In particular, the present invention relates to a bandgap reference voltage circuit that can obtain any output voltage.

(W) Conventional Technology A bandgap reference voltage circuit used to obtain a stable and highly accurate reference voltage is known. The circuit is described, for example, in Integrated Circuit Engineering I, page 23, published by Corona Co., Ltd. on January 30, 1980. The bandgap reference voltage circuit is as shown in FIG.
) is configured to generate an output reference voltage. The output voltage V of the output terminal (2) is output from the third transistor (3
>V□, (base-emitter voltage) and second resistor (4
) (however, the resistance value is the sum of the voltage V across both ends of R, ). Therefore, the value of the voltage V at both ends is determined.

First, the voltage V across the third resistor (5) R is Vg ”
” Vmm+ −vmgx=(xr/q) fl n(
It/L) -------(i). Therefore, the voltage V at both ends is Vt - (Rx/Ra) (KT/q> j2, (L
/ Eva (2), so the output voltage V is v-Vats + (Rx/Ra>(xT/q> 1
, (It/I - (3), the first term of equation (3) (
Vsas) has a negative temperature coefficient (approximately -2 mV/''C), so if the current is selected such that II > II so that the second term is positive, the overall temperature coefficient can be made zero. In the circuit shown in FIG. 2, a constant voltage that is not affected by temperature changes is obtained by canceling the temperature characteristics of the voltage across the second resistor (4) and the temperature characteristics of the voltage Vllll!j.

(c) Problems to be Solved by the Invention Now, the condition of equation (3) is satisfied when the output voltage V becomes approximately 1.2V.In order to obtain a higher value as the output voltage V, In order to do this, the circuit in FIG. 2 can be changed to the one shown in FIG. Resistor (4) and resistor (9) and third transistor (3
) and the diode (10), the temperature characteristics are canceled between the output terminal (11) and the output terminal (11).
) voltage is obtained. By adding a combination of a diode and a resistor to the circuit shown in FIG. 2 in this way, a voltage that is an integral multiple of the output voltage V can be obtained.

However, this method was problematic because it was not possible to obtain voltages other than voltages that were integral multiples of 1.2V.

(d) Means for Solving the Problems The present invention has been achieved in view of the above points, and includes a current generation circuit and a current mirror type that generates a bandgap current according to the current from the current generation circuit. It consists of a bandgap current generation circuit and a bandgap voltage generation circuit that generates a bandgap voltage according to the output current of the bandgap current generation circuit. In the bandgap reference voltage circuit which can obtain an output voltage of , the bandgap reference voltage circuit is characterized in that a resistor is connected in parallel to the diode in the bandgap current generating circuit.

(*) Effect According to the present invention, a bandgap reference voltage circuit that generates a desired reference voltage and has negative temperature characteristics is created, and is connected in parallel to the diode of the bandgap current generating circuit in the circuit. Since the resistor is connected, the temperature characteristics of the output reference voltage of the bandgap reference voltage circuit can be made flat.

(f) Embodiment FIG. 1 is a circuit diagram showing an embodiment of the present invention, (20)
is a fourth resistor (12) whose one end is connected to the constant current source (1);
) is the fifth resistor whose one end is connected to the constant current source (1), (1
3) is a diode whose one end is connected to the fifth resistor (12), and (14> is a temperature compensation resistor connected in parallel to the diode (13). In Fig. 1, the same as Fig. 2) The same reference numerals are given to the circuit elements.

First, the temperature coefficient shown in FIG. 1 is determined. The current Ill flowing through the diode (13) in FIG. 1 is as follows. Here, the change ΔI□ in the current Ill when the voltage VD changes due to a temperature change becomes Rh + R*. On the other hand, the current 11 flowing through the first transistor (6) in FIG. 2 is I* = (V- V□x)/Rt...
・・・・・・・・・(6) [However, R4 is the first resistor (8)
resistance value], and the change Δ■ becomes. The output voltage V' in Fig. 1 is converted to the output type FEV in Fig. 2.
In order to make them equal, it is necessary to make the currents flowing through the diode (13) and the first transistor (6) equal (1, l=1.). In addition, in order to do so, the molecule (R
Since e/(Ri+R-)) is smaller than 1, the (4th)
From formula and formula (6), Rx>Rs・R* / (Rs +R*)
・・・・・・・・・The relationship shown in (8) should be established. Then, from equation (8), ΔIII is Δ! It can be seen that the temperature change is large compared to . It is assumed that the changes in ΔVe and ΔV□ are equal. Further, since ΔvI) has a negative temperature coefficient, ΔIII becomes a positive temperature change. Therefore, the fourth resistor (
The change in the voltage across 20) is R4·Δ■□. on the other hand,
In the case of Figure 2, the change in voltage across the second resistor (4) is R8
・Δ■□. Here, since Δ■,1>Δ11, if the value of the resistor R4 is appropriately set to a value smaller than the value of the resistor R1, the voltage R4·Δ! , 1 and the voltage R1·Δ■1 can be made equal. In this way, an output voltage (1, 2 V) with a temperature coefficient of zero can be obtained at the output terminal (2) in FIG. 1, as in the case of FIG. 2.

Next, a case will be described in which an output voltage having a value lower than 1.2V is extracted. In this case, the value of the fourth resistor (20) in FIG. 1 is reduced depending on the desired voltage. Then, the temperature coefficient of the voltage across the fourth resistor (20) decreases, and the temperature characteristic of the output voltage V- becomes negative. Therefore, by adjusting the temperature compensation resistor (14) and increasing the current flowing through the fourth resistor (20), the temperature coefficient of the voltage across the fourth resistor (20) can be increased, and the output voltage The temperature coefficient of V can be made zero.

Next, a case will be described in which an arbitrary value of 1.2 V or more is obtained as the output voltage. There are two methods in this case. The first method is to connect a series circuit of a resistor and a diode so that the sum of the voltages at both ends is 1.2 V between the flipter of the second transistor (7) in Figure 1 and the constant current source (1). 0For example, if we want to obtain an output voltage of 5.6V, we will prepare four series circuits of the diodes and resistors, and obtain a voltage of 4.8V.
make.

Then, the remaining 0.8V can be generated by the fourth resistor (20) and the third transistor (3) in Fig. Make sure that the temperature characteristics of the voltage are flat.

In the second method, the output voltage V' in Fig. 1 is 1.12V (-
5,615V), and connect four resistors equal to the adjusted fourth resistor (20) and four diodes to the same locations as in the above case. , in this case, the value of the temperature compensation resistor is 5.6V.
Adjust so that the temperature characteristics of the voltage are flat.

FIGS. 4 and 5 show a specific circuit example and a specific numerical value example of the resistor when obtaining the above-mentioned output voltage of 5.6V.

In the case of FIG. 5, a voltage source is used instead of a current source, but it is preferable to use it when the value of the power supply voltage is lower than the value of the output voltage.

In the above explanation, the temperature coefficient of the resistor itself was ignored, but in the case of integrated circuits, the resistor has a positive temperature coefficient.However, in the case of integrated circuits, the temperature coefficient can be reduced to zero using the same method. You can.

(G) Effects of the Invention As described above, according to the present invention, in order to obtain a desired output voltage (that is, a voltage other than an integral multiple of 1.2V), first, a bandgap reference voltage circuit having negative temperature characteristics is used. create and
Since a temperature compensation resistor that provides positive temperature characteristics is connected to the circuit, the temperature coefficient of the output voltage can be made zero as a whole. Therefore, it is possible to provide a bandgap reference voltage circuit that can freely generate any output voltage.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, FIGS. 2 and 3 are circuit diagrams showing a conventional bandgap reference voltage circuit, and FIGS. 4 and 5 are another embodiment of the present invention. FIG. (1)...constant current source, (2)...output terminal, (
3)...Third transistor, (4)...Second resistor, (5)...Third resistor, (12)...Fifth resistor, (13>...Diode, (14) ...Resistance for temperature compensation.

Claims (4)

[Claims] (1) A current generation circuit, a current mirror type bandgap current generation circuit that generates a bandgap current according to the current from the current generation circuit, and a bandgap voltage generated according to the output current of the bandgap current generation circuit. a bandgap reference voltage circuit that generates a bandgap voltage generating circuit, and in which an arbitrary output voltage can be obtained by changing the value of a resistor in the bandgap voltage generating circuit, a diode in the bandgap current generating circuit; A bandgap reference voltage circuit characterized by connecting a resistor in parallel to the bandgap reference voltage circuit. (2) The band gap according to claim 1, wherein the band gap current generating circuit comprises two semiconductor elements and a load that flows a current according to a change in the forward voltage of the two semiconductor elements. Reference voltage circuit. (3) The bandgap according to claim 1, wherein the bandgap voltage generating circuit comprises a load having one end connected to the current generating circuit, and a transistor having a base connected to the other end of the load. Reference voltage circuit. (4) The temperature characteristic of the voltage generated across the load in the bandgap voltage generating circuit is larger than the temperature characteristic of the forward voltage of the transistor. Bandgap reference voltage circuit.